Electrical switching mechanism



Dec. 1, 1925.

s. H. CLARK ELECTRICAL SWITCHING MECHANISM Filed Aug. 5. 192a NNx Patented Dec. 1, 1925.

UNITED STATES PATENT orvics.

EDGAR H. CLARK, OF RICHMOND HILL, NEW YORK, ASSIGNOR TO WESTERN ELEC- TRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ELECTRICAL SWITCHING MECHANISM.

Application filed August 3, 1923.

To all whom it may concern.

Be it known that I, EDGAR H. CLARK, a citizen of the United States, residing at Richmond Hill, in the county of Queens and State of New York, have invented certain new and useful Improvements in Electrical Switching Mechanisms, of which the following is a tall, clear, concise, and exact description. 7 This invention relates to electrical switching mechanisms and more particularly to devices of this character employed in telephone exchange systems.

The object of the present invention an improved switching device for the intercontraction of electrical circuits wherein speed and etliciency are combined with certainty and reliability of operation.

A feature of the invention is the provision,

in a switch for interconnecting lines and trunks wherein the usual interference prevention devices are eliminated to secure greater speed, of means for guarding against the taking into use of any parts of the switch unless the connection can be success fully made. i I A further feature relates to the provision, in a coordinate switch where a plurality oi operating magnets are energized in conjunction to effect a connection, of means for first '1 "eparing a circuit for each necessary magnet and then reducing the resistance of such circuits to permit the magnets to operate.

Other and further features contemplated by this invention will be more fully understood trom the following detailed description and also from the appended claims.

Referring to the drawing, the figure therein shown illustrates a portion of a switch ing device employed as a line switch for in terconnecting subscribers telephone lines with trunk circuits and in which the features of the invention are embodied. The switch 105 is of the coordinate type in which the incoming lines appearing in. vertical rows are connectible to outgoing lines or trunks also appearing in vertical rows through the medium of: horizontal link circuits. The contacts in the vertical rows are prepared by vertical magnets which operate bars, one being provided for each row. The horizon tal links with which connection is made by the preparedcontacts of the several vertical rows are operated also by individual operating magnets and bars. The construction and Serial No. 655,385.

operation of a switch of this character is disclosed in the patent to Goodrum and Reynolds, No. 1,515,735, issued November 18, 19241.

The line switch 105 which serves to extend incoming subscribers lines in a telephone system to trunks which lead to other switches may have any desirable capacity. The illustrati-on shows 1 subscribers lines 100, 101, 102 and 103 incoming and appearing in the vertical rows of contacts 112 and 113. The line 101 and 103 both appear in the vertical row 112. The line 101 has access to a group of horizontal links including the links 106, 107 and 108, while the line 103 has access to another group of horizontal links including links 109, 110 and 111. The lines 100 and 102 occupying the second vertical row 113 have access respectively to these two groups of horizontal links. In a similar manner other groups of horizontal links may be provided in the same switch in which appear other subscribers lines. Likewise, there may be as many vertical rows for receiving incoming subscribers lines as desired.

Inaddition to the subscribers lines, the switch 105 also contains a plurality of verti-, cal rows of contacts representing outgoing trunks. Two trunks, 137 and 138 only are shown occupying the vertical rows of contacts 114 and 115. It will be noted that each of the trunks has an appearance'before every horizontal link in every group of the switch whereby any trunk may be reached through the medium of any link.

It is customary practice to provide line switches and other preliminary switching devices in telephone systems with non-inter.- :Eering circuit arrangements in order to eliminate as far as possible the likelihood of double connections; Many plans have been. suggested and worked out for accoi'nplishing this purpose. To prevent a double connection, however, it is necessary to provide ad ditional equipment and circuits and sometimes to regulate the order and degree of availability with which calling lines may appropriate trunks. In the present arrangement the switch to a large extent is freed from these additional circuitcomplr cations. This has been done in order to speed up the operation of the switch and to give each and every line anequal opportunity with all others ln'obtainlng connection to J tinue to a successful completion.

an outgoing trunk. Although remote, there is a possibility that on rare occasions, two subscribers calling simultaneously may have their line connected to the same trunk, in which case it would be required that they hang up their receivers and again initiate the call in order to get a clear connection.

To guard against the possibility of a double connection while at the same time retaining all the advantages to be had in a switch where the complicated non-interfering eouipment is provided, the present invention is so designed that the several operations which take place sequentially are not commenced until it has first been ascertained that the connection will be successful. In other words, the switch is not started in operation in response to a call, unless it is known that once having started, it may con- 1 detailed description of the operation of the switch and its related circuits will now be i n.

For this purpose, assume that the sub- 7 scriber of line 101 wishes to initiate a call.

On removing his receiver from the switch hook, a circuit is completed from battery to the. winding of line relay 120, inner contact f cu -o re y 1 ove t e ring c n o of the line and returns over the, tip conductor through the outer contact of relay 121 to ground. Relay 120 operates and a circuit is completed from battery through the winding of the vertical operating magnet 116, conductor 144, outer contact of relay 120, conductor 145, through the windings of relay 122 to ground. The relay 122 operates but the combined resistance of its windings is so great that the vertical operating magnet 116, cannot operate. Furthermore, a circuit is closed from battery, through me winding of vertical operating magnet 118, assuming the first trunk 13'? to be idle, upper back contact of trunk relay 135., conductor 147, inner contact of line relay 120, conductor 146, through the windings of relay 12.3 to ground. Relay 123 operates, but due to its resistance, the vertical magnet 118 does not receive sufficient current to operate. Thus, on the operation of the line relay 120., the relays 122 and 123. are included in series it the v ti al opera ing m g ets to te the windings and circuits of these magnets. Since they are found in operable condition, he relay .122 a d. 1.23. ope e t th acnets are prevented from operating at this time due to the high resistances of the relays. It may be noted a s time hat. the e ys 2 12 a d 24 r common to th group of horizon al Link cont ning e links 106,- 1.07, 10.83 etc-s betore whi h the all ng lin swears. In similar manner. rel ys 12 28 an 12.9 are 01. 11.1 .011 t t other group of h rizontal link sh e- Wi h rol er- 1.22 and. 123 perat d. jo nt-13 a circuit is closed from ground through the contact of relay 123, windings of relay 124, outermost contact of relay 122, conductor 148, front contact of relay 130, assuming the first horizontal link 108 to be busy, back contact of relay 1.31, assuming the link 10? to be idle, right hand winding of the horizontal operating magnet 133 to battery. The relay 124- actuates in this circuit, but due to its resistance, surficient current will not flow to operate the iorizontal magnet 183. Thus, the operation of relay 124 serves as an indication that there is an idle horizontal link in the desired group over which connection may be had and that the circuit and winding of the operating magnet for this link are in proper condition. However, the horizontal magnet is not operated at the time.

Relay 124 in operating, modifies the circuits of the vertical magnet 116 and 118 in such a manner as to appreciably diminish the resistances in order to permit these mas nets to operate. For example, the circuit oi the vertical magnet 116 may now be traced over conductor 144, contact of relay 120, conductor 145, right-hand winding of relay 122, outer right-hand contact of relay 124 to ground at the contact of. the slow op crating relay 134. The left-hand winding of relay 122 having been excluded, the ver tical magnet 116 receives sutlicient current and operates to prepare all the contacts in the vertical relay 112. The circuit of mag net 118 which is also modified. may now be followed over the conductor 147, through the Contact of relay 120, conductor 146, lefthand windingot relay 123, inner right contact of relay 124 to ground at the contact of relay 1,34. The right-hand winding of relay 123, having been excluded from the circuit, the magnet 118 operates to prepare all contacts in the vertical row 114. w. nen both vertical magnets 11.6 and 118 operate jointly, the circuit oi? the horizontal operating magnet 133 is modified so that now extends from battery through the right-hand winding of said magnet, thence over conductor 148 through the outermost contact of relay 122, right-hand v-rinding of relay 124, left contact of d relay, conductor 149, contact of magnet 116, upper contact of magnet 118 to ground. The lefthand winding of relay 124 i;v excluded from this circuit and consequently the resistance in series with magnet 13.3 is reduced to such an extent that'the magnet becomes. operated.

Returning to the pointy where the vertical perating, magnet, 118. is. energ e a c rcui may be emu fro g o nd h ough h o er front c act of; said. m gnet, thence ve the le ve conduct r .150 of he tr k 137, back contact of l w relea role-y 1 .25 ther contact of. relay 1;, Winding f r lay 43 to battery- Bl y n suita le ill) manner may serve to initiate the operation of another switch similar to the switch 105, as for the purpose of associating the trunk 137 with a central otfice sending mechanism. Relay 143, in operating, looks through its winding and inner contact through ground at the outer right back contact of relay 139. Relay 143 also closes a circuit for the slow release relay 142. Relay 142 operates and through its front contact applies a holding ground potential to the sleeve conductor 150 of the trunk. Later, when the horizontal operating magnet 133 is operated as described, the connection is extended from the line 101, over the horizontal link 107 to the idle outgoing trunk 137. Immediately that this connection is effected, a circuit is closed from battery through the windings of magnet 133, winding of relay 131 over the test conductor of the link 107 through contacts of switch 105 to the grounded sleeve conductor 150. Relay 131, however, does not operate at this time since it is shunted by the original operating circuit of magnet 133 which leads to ground through the contacts of the vertical magnets 116 and 118.

It will also he noted that when magnets 116 and 118 were operated to apply ground potential to the conductor 149, a circuit was therehy completed for the relay 134. Relay 134 being slow to operate, requires an interval in which to attract its armature. 'When, however. relay 134 finally operates, it removes ground potential from the contacts of relay This includes the secondary windings of relays 122 and 123 in the circuits of the vertical operating magnets 116 and 118 and consequently these magnets become deenergized. As soon as the vertical magnets 116 and 118 release, direct ground is removed from the conductor 148 and the shunt around the winding of relay 131 is consequently opened. Hence, relay 131 operates in series with magnet- 133 and both are locked to the grounded sleeve conductor 150 through contacts of relay 142. Relay 131 in operatin extends the start wire 148 through to the horizontal magnet of the next link circuit in order that this circuit may now be taken for the establishment oi a subsequent connection.

At the time the switch is operated a circuit is also closed from the grounded con ductor 150 through the contacts of the switch over the sleeve conductor 152, Wind ing of cut-ofi' relay 121 to battery. Relay 121 operates and opens the circuit of relay 120 which in turn disconnects the control relays 122 and 123 and these relays become released.

As soon as the vertical operating magnet 118 releases when the connection is effected, a circuit is closed from ground over conductor 150 through the lower back contact lay 135 is deenergized.

of magnet 118, upper winding of relay 135 to battery. Relay 135 operates and extends the start conductor 147 through to the next vertical operating magnet 119. It the next trunk 138 happens to be busy, relay 136 will be operated in a similar manner and the start conductor is extended still further to the next trunk.

As soon as the subscribers line 101 is extended through the line switch 105 to the left-hand windings of the repeating coil 140 in the trunk 137, the supervisory relay 141 is energized. Relay 141 at its contact closes a substitute circuit for the slow relay 142, relay 143 having deenergized to open the original holding circuit.

When the connection is no longer required, the calling subscriber by replacing his receiver on the switchhook opens the cir cuit of the supervisory relay 141. Relay 141 releases and opens the circuit of slow relay 142. After an interval, relay 142 deenergizes and removes ground from the holding conductor 150, whereupon the magnet 133 and relay 131 become deenergized and the connection through switch 105 is released.

Should one of the lines 100 or 102 in the vertical row 113 initiate a call, the vertical operating magnet 117 would'he taken into use in connection with one of the trunk vertical magnets 118 and 119 in a manner identically the same as that already described in detail.

\Vhere the start wire 147 depends upon the contacts of the trunk relays 135, 136, etc, it is necessary to preserve the continuity of. this start wire should a preceding trunk hecome idle at the instant when one of? the silC- ceeding trunks was being taken into use. To this end, a common relay 153 is provided. It the trunk 137, having been previously engaged, is released at the instant the succeeding trunk 138 is being taken for use, the relay 135 if permitted to release would disrupt the start wire 147. The instant the trunk .37 becomes idle, ground is removed from conductor 150 and the upper winding of re- 7 Since, however, at this time, the start wire 147 is grounded, a circuit is closed from battery through the contact oil? relay 153. lower winding andv i.unor lower contact of relay 135 to the grounded conductor 147. Therefore, the re lay 135 is held energized temporarily to pre serve the start wire 147 until the succeeding trunk has been fully selected.

Should all trunks be simultaneously busy, a circuit is closed from, battery through the winding of relay 153, over the lower front contacts of relay 135, 136, etc. in series to ground.

For an understanding of the general manner in which the trunks may be extended to senders and for other details not disclosed &

herein, reference is made to the patent to S. B. Williams, No. 1,517,381, issued December 2, 192-1.

lVhat is claimed is:

1. The combination in a switching device of a plurality of operating magnets 'coac'ting jointly to effect a connection, means for closing circuits for each 0t said magnets without operating the same. and means for thereupon altering said circuits to permit said magnets to operate.

2. The combination in a switching device of a plurality ot operating magnets coacting with each ot ier to ei'l'ect connections, means for closing circuits for each of said magnets without operating'th'e same, and means for modifying the resistances 01 said circuits to permit said magnets to operate.

3. The combination in a switching device of a plurality of operating magnets coa'cting with each other to effect connections, means for preparing circuits for each of said magnets to ascertain it they are operative, said magnets remaining inert in said circuits, and means for thereupon altering said circuits to decrease the resistances thereof to permit the operation of said magnets.

1. The combination in a switching device of a plurality of operating magnets coacting jointly to establish connections, means for preparing circuits to test the condition of said magnets without operating the same, and means responsive to the test for thereupon altering said circuits to cause the oporation of said magnets.

5. The combination in a switching device of a plurality of electromagne'ts coacting jointly to effect connections, means for preparing circuits for said magnets without actuating the same, means for testing the condition of said circuits, and means responsive to the test for thereupon altering such circuits to cause the operation of'said. magnets.

6. The combination in a switcl'iing device of a plurality of operating magnets co'a'cting jointly to establish a connection, means for closing circuits for 'each of said magnets without operating the same, and means for altering the resistances of said circuits to permit said magnets to operate in a "definite order with respect to each other.

7;. The combination with incoming lines and outgoing lines of a switching device including link circuits for interconnecting said lines, electromagnets coacting with each other to operate said switching device, means for closing circuits for each of said magnets without operating the same, and means after the circuits have been prepared for altering the same to permit said magnets to operate.

8. The combination with incoming lines and outgoing lines, of a switching device l'iavin'g link circuits for interconnecting the incoming lines and the outgoing lines, a plural'ity of magnets cooperating to actuate said switching device, means for preparing circuits for said magnets to determine if there is an available link and an available outgoing line, said magnets remaining inert to said circuits, and means for altering the circuits to permit the operation of said magnets.

9. A switching device having vertical rows of contacts, lines appearing in said vertical rows of contacts, trunks appearing in other of said rows, link circuits for interconnecting said lines ana trunks, a plurality of magnets cooperating with each other to actuate said contacts for effecting a connection, means for closing circuits for said magnets without operating the same, and means for modifying said circuits to cause the operation of said magnets.

In witness whereof, I hereunto subscribe my name this 27 day of July, A. 1)., 1923.

EDGAR I-I. CLARK. 

